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    <title>ShellCheck: SC2312 – Consider invoking this command separately to avoid masking its return value (or use '|| true' to ignore).</title>
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    <h1>SC2312 – ShellCheck Wiki</h1>
    <a href="https://github.com/koalaman/shellcheck/wiki/SC2312">See this page on GitHub</a>
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    <h2
id="consider-invoking-this-command-separately-to-avoid-masking-its-return-value-or-use--true-to-ignore">Consider
invoking this command separately to avoid masking its return value (or
use '|| true' to ignore).</h2>
<p>This is an optional suggestion enabled with
<code>shellcheck -o check-extra-masked-returns</code> or
<code>enable=check-extra-masked-returns</code> in a
<code># shellcheck</code> directive or <code>.shellcheckrc</code>.</p>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC2312.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="bu">set</span> <span class="at">-e</span></span>
<span id="cb1-2"><a href="SC2312.html#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="bu">cd</span> <span class="st">&quot;</span><span class="va">$(</span><span class="ex">get_chroot_dir</span><span class="va">)</span><span class="st">/etc&quot;</span></span>
<span id="cb1-3"><a href="SC2312.html#cb1-3" aria-hidden="true" tabindex="-1"></a><span class="fu">tar</span> xf <span class="st">&quot;</span><span class="va">${config}</span><span class="st">&quot;</span></span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC2312.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="bu">set</span> <span class="at">-e</span></span>
<span id="cb2-2"><a href="SC2312.html#cb2-2" aria-hidden="true" tabindex="-1"></a><span class="va">dir</span><span class="op">=</span><span class="st">&quot;</span><span class="va">$(</span><span class="ex">get_chroot_dir</span><span class="va">)</span><span class="st">&quot;</span></span>
<span id="cb2-3"><a href="SC2312.html#cb2-3" aria-hidden="true" tabindex="-1"></a><span class="bu">cd</span> <span class="st">&quot;</span><span class="va">${dir}</span><span class="st">/etc&quot;</span></span>
<span id="cb2-4"><a href="SC2312.html#cb2-4" aria-hidden="true" tabindex="-1"></a><span class="fu">tar</span> xf <span class="st">&quot;</span><span class="va">${config}</span><span class="st">&quot;</span></span></code></pre></div>
<h3 id="correct-code-with-correction">Correct code: (with
correction)</h3>
<div class="sourceCode" id="cb3"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb3-1"><a href="SC2312.html#cb3-1" aria-hidden="true" tabindex="-1"></a><span class="bu">set</span> <span class="at">-e</span></span>
<span id="cb3-2"><a href="SC2312.html#cb3-2" aria-hidden="true" tabindex="-1"></a><span class="va">dir</span><span class="op">=</span><span class="st">&quot;</span><span class="va">$(</span><span class="ex">get_chroot_dir</span><span class="va">)</span><span class="st">&quot;</span></span>
<span id="cb3-3"><a href="SC2312.html#cb3-3" aria-hidden="true" tabindex="-1"></a><span class="kw">[[</span> <span class="ot">-d</span> <span class="st">&quot;</span><span class="va">${dir}</span><span class="st">&quot;</span> <span class="kw">]]</span> <span class="kw">||</span> <span class="bu">exit</span> 1</span>
<span id="cb3-4"><a href="SC2312.html#cb3-4" aria-hidden="true" tabindex="-1"></a><span class="bu">cd</span> <span class="st">&quot;</span><span class="va">${dir}</span><span class="st">/etc&quot;</span></span>
<span id="cb3-5"><a href="SC2312.html#cb3-5" aria-hidden="true" tabindex="-1"></a><span class="fu">tar</span> xf <span class="st">&quot;</span><span class="va">${config}</span><span class="st">&quot;</span></span></code></pre></div>
<h3 id="rationale">Rationale:</h3>
<p>In the problematic example, the exit code for
<code>get_chroot_dir</code> is ignored because it is used in a command
substitution in the argument of another command.</p>
<p>If the command shows <code>error: Can't determine chroot</code> and
exits with failure without outputting a directory, then the command
being run will be <code>cd "/etc"</code> and the script will proceed to
overwrite the host system's configuration.</p>
<p>By assigning it to a variable first, the exit code of the command
will propagate into the exit code of the assignment, so that it can be
checked explicitly with <code>if</code> or implicitly with
<code>set -e</code>.</p>
<h3 id="exceptions">Exceptions:</h3>
<p>If you don't care about the command's exit status, or already handle
it through a side channel like
<code>&lt;(cmd; echo $? &gt; status)</code>, then you can either <a
href="ignore.html">ignore</a> the suggestion with a directive, or use
<code>|| true</code> (or <code>|| :</code>) to suppress it.</p>
<h3 id="related-resources">Related resources:</h3>
<ul>
<li>Help by adding links to BashFAQ, StackOverflow, man pages, POSIX,
etc!</li>
</ul>
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